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(1) Field of the Invention
The present invention relates to an adjustment mechanism for adjusting the height of a work surface of a workstation. In particular, the present invention relates to an adjustment mechanism which uses rotation of a threaded member to adjust the height of the work surface. The threaded member is rotated by a handle through an operating mechanism having sprockets with different diameters which allows the threaded member to rotate at a faster rate than the rate the handle is rotated. The adjustment mechanism uses a spring to compensate for the load on the adjustment mechanism and to allow the user to rotate the handle using less force.
(2) Description of the Related Art
The related art has shown various adjustable height workstations which use a rotating, threaded member and a stationary nut to adjust the height of the table or workstation. U.S. patents which are illustrative are U.S. Pat. No. 1,943,280 to Arnold; U.S. Pat. No 5,022,327 to Solomon; U.S. Pat. No. 5,447,099 to Adams et al; U.S. Pat. No. 5,685,510 to Frankish; U.S. Pat. No. 5,845,590 to Seidel; U.S. Pat. No. 5,890,438 to Frankish; and U.S. Pat. No. 5,941,182 to Greene.
Arnold describes a table having four adjustable legs. Each leg contains an adjustment mechanism which includes a screw and a stationary nut. A sprocket is mounted at the end of each screw. The sprockets of all four adjustment mechanisms are connected together by a chain. The chain passes about a drive sprocket which is mounted on a crank or handle. When the handle is rotated, the drive sprocket rotates which rotates the sprockets and screw of each adjustment mechanism.
Solomon describes an adjustable overbed table. A rotatable screw shaft is used to adjust the table. A crank handle is attached to bevel gears which rotate bevel gears on the end of the rotatable screw shaft.
Adams et al describes a height adjustment mechanism for tables. The drive means for the mechanism comprises a gear box, a jack screw and a jack nut with a crank for rotating the jack screw by means of a pair of bevel gears. One of the bevel gears is secured to the end of the jack screw.
Frankish ""510 and ""586 describe a height adjustment system which includes a work-top member supported by a plurality of height adjustable legs. The legs have a stationary first leg part and a movable second leg part. A rotatable shaft extends vertically within the second leg part and has an upper portion and a lower portion. The lower portion is in the form of a screw. A pair of half nuts are positioned within the second leg part and act to position the screw within the second leg part. Vertical movement of the second leg part is also guided by at least one (1) linear bearing spaced between the first and second leg parts. The upper portion of the rotatable shaft is housed within a tubular member. A compression spring may be provided around the tubular member within the second leg part. The compression spring is retained between the lower part of the gear box housing and the base plate at the lower end of the first leg part. The compression spring is not rotatable and is fully supported within the second leg part to prevent buckling of the first leg part. The compression spring can compensate for external loads in the leg. The second leg part is secured at the upper end to the right angle gear box. The gear box includes a crown gear mounted on the upper end of the vertical shaft and a pinion gear engageable with the crown gear. The pinion gear is mounted on the end of a rotatable horizontal shaft which extends in a horizontal direction out of the gear box. The horizontal shaft is rotated by a drive mechanism comprising a winding mechanism including a rotatable drive shaft linked by universal joints and a first rotatable transmission member to a drive shaft. The drive shaft is connected to a rotatable drive transmission member which is connected to the horizontal shaft. A retractable handle is connected to the drive shaft for operating the winding mechanism. When the screw is rotated, the second leg part, gear box and work-top member move vertically relative to the first leg part.
Seidel describes an adjustable height table assembly. The base assembly includes a housing with a vertical leg extending upward and attached to the table top and movable within the housing. The housing also includes a pair of vertical guide members spaced from each other with a slide assembly slidably mounted to the guide members. The vertical leg is fixably mounted to the slide assembly. The vertical adjustment mechanism for the assembly includes a rotatable screw extending through a passage defined by the vertical leg. A tubular member is mounted within the housing between the vertical guide members, and receives the lower portion of the threaded member. A fixed nut is mounted toward the upper end of the tubular member and is threadably engaged with the threads of the screw. The table top support further includes an arm to which the table top is secured. The arm defines an axial passage, which is in communication with the passage formed in the vertical leg through which the screw extends. A driven sprocket is mounted to the screw toward its upper end, and a drive sprocket is rotatably mounted to the arm below the table top. A chain is engaged with the drive sprocket and with the driven sprocket, and a manually operable crank provides rotation of the drive sprocket, which is transferred through the chain and the driven sprocket to impart rotation to the screw and to thereby adjust the height of the table top.
Greene describes a vertically adjustable table which is adjustable using a crank handle. The leg assemblies include a stationary part and a movable part. The lifting mechanism comprises a ball screw and a ball nut. The ball nut is rigidly affixed to the stationary part of the leg assembly and the ball screw rotates in the ball nut. The table top is raised or lowered depending on the direction of rotation of the screw. The table uses a pulley and cable arrangement to ensure that the table raises and lowers in a level manner which obviating the need for a chain and sprocket. A miter gear set is used to convert horizontal torque applied by the user on the handle to the vertical torque needed to rotate the ball screw. The gear box mechanism is securely attached to a bracket which is secured to the movable portion of the leg assembly and to the underside of the table. The gear box mechanism is also securely attached to the ball screw.
Also of interest are U.S. Pat. No. 4,635,492 to Uebelhart; U.S. Pat. No. 5,088,421 to Beckstead and U.S. Pat. No. 5,282,593 to Fast which show the use of a motor to rotate the threaded member to adjust the height of a table or workstation.
There remains the need for an adjustment mechanism for use in adjusting the height of a work surface of a workstation which has a simple operating system which is manually operated by a handle which allows for fewer rotations of the handle by the user to obtain the required height adjustment and which uses a spring to compensate for a load on the work surface.
The present invention relates to an adjustment mechanism for vertically adjusting a work surface of a workstation, which comprises: a stationary first member defining a longitudinal axis of the mechanism; a movable second member connected to the work surface of the workstation and being movable relative to the stationary first member in a substantially vertical direction along the longitudinal axis of the mechanism; a support fixably mounted to the stationary first member and having a threaded opening extending substantially along the longitudinal axis of the mechanism; a threaded member rotatably connected to the movable second member and extending through the threaded opening of the support wherein threads of the threaded member engage threads of the threaded opening; a resilient means extending between the first member and the second member substantially along the longitudinal axis of the mechanism and tending to bias the members apart; one driven sprocket fixably mounted on the threaded member adjacent to the work surface; one drive sprocket directly connected to the driven sprocket and mounted on a shaft rotatably mounted on the work surface, the drive sprocket having a diameter greater than a diameter of the driven sprocket; means for directly connecting the driven sprocket and the drive sprocket; and means for rotating the shaft and the drive sprocket wherein when the drive sprocket rotates, the driven sprocket is rotated which rotates the threaded member in the threaded opening of the support such that the second member is moved relative to the first member.
Further, the present invention relates to a system for adjusting a height of a work surface of a workstation, which comprises: a primary adjustment mechanism including: a stationary first member defining a longitudinal axis of the mechanism; a movable second member connected to the work surface of the workstation and being movable relative to the stationary first member in a substantially vertical direction along the longitudinal axis of the mechanism; a support fixably mounted to the stationary first member and having a threaded opening extending substantially along the longitudinal axis of the mechanism; a threaded member rotatably connected to the movable second member and extending through the threaded opening of the support wherein threads of the threaded member engage threads of the threaded opening; a resilient means extending between the first member and the second member substantially along the longitudinal axis of the mechanism and tending to bias the members apart; one driven sprocket fixably mounted on the threaded member adjacent to the work surface; and one alignment sprocket mounted on the threaded member adjacent the work surface; at least one secondary adjustment mechanism including: a stationary first member defining a longitudinal axis of the mechanism; a movable second member connected to the work surface of the workstation and being movable relative to the stationary first member in a substantially vertical direction along the longitudinal axis of the mechanism; a support fixably mounted to the stationary first member and having a threaded opening extending substantially along the longitudinal axis of the mechanism; a threaded member rotatably connected to the movable second member and extending through the threaded opening of the support wherein threads of the threaded member engage threads of the threaded opening; a resilient means extending between the first member and the second member substantially along the longitudinal axis of the mechanism and tending to bias the members apart; and an alignment sprocket mounted on the threaded member adjacent the work surface; one drive sprocket directly connected to the one driven sprocket of the primary adjustment mechanism and mounted on a shaft rotatably mounted on the work surface, the drive sprocket having a diameter greater than a diameter of the driven sprocket of the primary adjustment mechanism; means for directly connecting the drive sprocket of the primary adjustment mechanism and the driven sprocket; and means for rotating the shaft and the drive sprocket wherein as the drive sprocket rotates, the driven sprocket is rotated which rotates the threaded shaft of the primary adjustment mechanism and the alignment sprocket of the primary adjustment mechanism; and means for connecting the alignment sprocket of the primary adjustment mechanism to the alignment sprocket of the secondary adjustment mechanism so that when the threaded shaft and the alignment sprocket of the primary adjustment mechanism rotate, the alignment sprocket and threaded member of the secondary adjustment mechanism rotate so that the primary adjustment mechanism and the secondary adjustment mechanism move at substantially the same rate.
Still further, the present invention relates to a method for adjusting a height of a work surface of a workstation which comprises the steps of: providing an adjustment mechanism for the work surface of the workstation, the adjustment mechanism including a stationary first member defining a longitudinal axis of the mechanism; a movable second member connected to the work surface of the workstation and being movable relative to the stationary first member in a substantially vertical direction along the longitudinal axis of the adjustment mechanism; a support fixably mounted to the stationary first member and having a threaded opening extending substantially along the longitudinal axis of the adjustment mechanism; a threaded member rotatably connected to the movable second member and extending through the threaded opening of the support wherein threads of the threaded member engage threads of the threaded opening; a resilient means extending between the first member and the second member substantially along the longitudinal axis of the mechanism and tending to bias the members apart; one driven sprocket fixably mounted on the threaded member adjacent to the work surface; one drive sprocket directly connected to the driven sprocket and mounted on a shaft rotatably mounted on the work surface, the drive sprocket having a diameter greater than a diameter of the driven sprocket; means for directly connecting the driven sprocket and the drive sprocket and means for rotating the shaft and the drive sprocket wherein when the drive sprocket rotates, the driven sprocket is rotated which rotates the threaded member in the threaded opening of the support such that the second member is moved relative to the first member; and activating the means for rotating the shaft and drive sprocket such that the shaft and drive sprocket rotate which rotates the threaded member which moves the second member relative to the first member which vertically adjusts the work surface.
The adjustment mechanism of the present invention allows for quick and relatively effortless adjustment of a work surface of a workstation. The adjustment mechanism includes a stationary outer member and a movable inner member telescopingly mounted in the outer member. The outer member is mounted with a lower end adjacent the ground surface. The inner member is mounted with a lower end in the upper end of the outer member and the upper end adjacent to and in contact with the underneath surface of the work surface. A screw is rotatably connected at the first end to the upper end of the inner member. The second end of the screw extends down through a nut cap fixably mounted on one end of a nut support. The other end of the nut support is mounted on the lower end of the outer member. A spring is mounted around the screw and the nut support and extends between the lower end of the outer member and the upper end of the inner member.
A driven sprocket is fixably mounted on the first end of the screw. A drive sprocket is mounted on a shaft spaced apart from the driven sprocket preferably toward the front edge of the work surface. The driven sprocket is connected by a chain to the drive sprocket. The diameter of the drive sprocket is greater than the diameter of the driven sprocket. A handle for operating the adjustment mechanism is connected to the shaft. As the handle is rotated, the driven and drive sprockets rotate which rotates the screw. Due to the larger diameter of the drive sprocket, the driven sprocket will rotate at a faster rate than the handle. As the screw rotates, it moves up and down in the top nut causing the inner member to move up and down in the outer member, thus raising or lowering the work surface. The spring extending between the lower end of the outer member and the upper end of the inner member, compensates for the load on the adjustment mechanism and allows the handle to be rotated using a reasonable force even with a load on the work surface and allows the screw to rotate at a faster rate than the handle.
An alignment sprocket is preferably fixably mounted on the upper end of the screw. The alignment sprocket is connected by a chain to the alignment sprockets of the secondary adjustment mechanisms for the workstation. The alignment sprockets ensure that all the adjustment mechanisms of a single workstation adjust the work surface at the same rate. The alignment sprocket also allows a single operating mechanism to be used to adjust multiple adjustment mechanisms of an adjustment system provided on a single workstation.
The adjustment mechanism of the present invention allows for adjusting a work surface of a workstation a greater distance in fewer rotations of the handle. The adjustment mechanism also allows for the use of a reasonable force to rotate the handle regardless of the position of the work surface. The adjustment mechanism also allows for the application of a manageable force on the handle to adjust the work surface even when a load is applied to the work surface.
The substance and advantages of the present invention will become increasingly apparent by reference to the following drawings and the description.